Fibrous ceramic monoliths made from multi-phase ceramic filaments

Abstract

A method for producing composite ceramic material is provided wherein a core ceramic structure is produced and simultaneously enveloped with a sleeve of similar material.

1. A monolith having an inner region and a peripheral region and comprising a plurality of multi-phase filaments, the filaments each having a cell phase and a boundary phase, whereby said boundary phase is concentrically arranged about the cell phase and coaxial to the cell phase, whereby the peripheral region of the monolith comprises a set of filaments wherein a majority of the peripheral region filaments consist of a 80/20 cell/boundary phase volume percent and the inner region of the same monolith comprises a set of filaments wherein a majority of the inner region filaments consist of ≦75 volume percent cell phase and ≧25 volume percent boundary phase. 
     
     
       2. The monolith as recited in  claim 1  wherein no space exists between the arranged filaments. 
     
     
       3. The monolith as recited in  claim 1  wherein the filaments have cross sections having the shapes of triangles or squares or rectangles or trapezoids or hexagons or combinations thereof and no void space exists between the filaments. 
     
     
       4. The monolith as recited in  claim 1  wherein the cell phase and the boundary phase contain oxides selected from the group consisting of ZrSiO 4 , Al 2 O3, mullite, yttrium aluminum garnet, and combinations thereof. 
     
     
       5. The monolith as recited in  claim 1  wherein the cross section of the cell phase has a radius of curvature of between approximately 0.02 a and 0.2 a whereby “a” is the dimension of the side of a polygon that is the cross section and wherein the boundary phase cross section has a polygon with a different radius of curvature. 
     
     
       6. The monolith as recited in  claim 1  wherein the inner region contains filaments with at least approximately five volume percent lower cell phase compared to the boundary phase of the filaments. 
     
     
       7. The monolith as recited in  claim 1  wherein a surface of the boundary phase further comprises a coating to impart a texture to the filament. 
     
     
       8. The monolith as recited in  claim 7  wherein the texture increases friction between adjacent filaments. 
     
     
       9. The monolith as recited in  claim 1  wherein the inner region of the same monolith comprises filaments with <50 volume percent cell phase and >50 volume percent boundary phase. 
     
     
       10. The monolith as recited in  claim 1  wherein filaments of particular cell phase and boundary phase percentages comprise the inner region and filaments of different cell phase and boundary phase percentages comprise the monolith peripheral region so as to achieve desired strength and durability of said monolith. 
     
     
       11. A monolith having an inner region and a peripheral region consisting of a plurality of multi-phase filaments, the filaments each having a cell phase and a boundary phase, whereby the filaments residing in the peripheral region of the monolith consist of a 80/20 cell/boundary phase volume percent and the filaments residing in the inner region of the same monolith consist of ≦75 volume percent cell phase and ≧25 volume percent boundary phase.